(1) Field of Invention
The present invention relates to a gyratory finishing machine having a curvilinear finishing chamber, and more particularly refers to such an apparatus having a vertically oriented gyratory motion-producing assembly and power driving means so mounted that the coupling-speed ratio may be readily changed, and the power driving means may be readily removed for repair or replacement.
(2) Prior Art
Gyratory finishing machines having vertically oriented motors and eccentric weight assemblies are known in the art. Such machines are used for various forms of finishing, such as abrading, burr removal, burnishing, polishing, and grinding. Such machines are disclosed and claimed in U.S. Pat. No. Re. 27,084, 3,400,495, 3,423,884, 3,435,564, 3,466,815, 3,606,702, and 3,633,321. In such apparatus, the motor is permanently affixed to the inside of a tubular frame, and the eccentric weights are mounted on the motor shaft. Machines of the type described are vibrated in such a manner that a gyratory motion is produced, that is, a motion wherein the axis of the vibrating portion of the machine is inclined from the vertical and describes substantially a pair of conical surfaces as it gyrates. As a result of the gyratory motion, when material such as parts and/or finishing material are placed in a chamber having a bottom of arcuate cross-section which is caused to vibrate by the gyratory motion, orbital motion is imparted to the material so that it moves upwardly at the peripheral portion of the chamber and downwardly at the inner portion of the chamber. This results in relative movement between the finishing material and parts, causing the parts to be finished. Additionally, by the use of a proper phase relationship between the eccentric or unbalance weights, varying degrees of precession or linear progression of the material and parts are caused circumferentially around the annular finishing chamber.
In most prior art machines the gyratory motion-producing parts of the apparatus are mounted in a housing generally in the form of a vertical tube. The motor is bolted to the inside wall of the tubular housing, generally at a central portion thereof, and the eccentric or unbalance weights are directly mounted on the two opposite external ends of the motor shaft. Because of the exceptionally strong gyratory forces set up by rotation of the eccentric weights, the motor must be specially designed and must have extremely heavy duty bearings. Such specially built motors are very expensive. Moreover, because of the extreme stresses to which the motor is subjected, the motors must be repaired or replaced at rather frequent intervals. In order to remove an internally mounted motor of the type described, the entire apparatus must be disassembled. This is a costly and time-consuming process. Additionally, when it is necessary to reline the tub or finishing chamber, the motor must be removed and the entire assembly sent to another place for relining.
Prior art machines have also been constructed utilizing a separate shaft having the eccentric weights mounted thereon, a motor mounted on the housing, having belt and pulley drive, and with a pulley mounted on the shaft intermediate the bearings. In such an apparatus it is difficult to change the pulleys and belt in order to achieve various driving ratios, since the apparatus must be disassembled to get at both the pulleys and the belt. Moreover, it is difficult to remove the motor from within the tube.
Gyratory finishing apparatus of the type described has been disclosed in which the motor is mounted externally of the apparatus on a fixed and non-vibrating portion of the frame. In one such structure disclosed in U.S. Pat. No. 3,693,298, the motor is mounted on a fixed portion of the frame of the finishing machine coupled to the floating or gyratory portion by means of pulleys and a belt, one pulley being mounted on the motor and the other on the vertical gyratory shaft supporting the eccentric weights. In such structure a vibratory force is applied to the belt by the gyrating pulley.
Another such structure wherein the motor is rigidly mounted on a fixed portion of the frame of the finishing machine is shown in Pool U.S. Pat. No. 3,708,918. It is obvious that, in such a structure wherein the vibratory force is applied to the belt by the gyrating pulley, or vice versa, much is left to be desired from the standpoint of engineering and economic efficiency, as will immediately be apparent to anyone skilled in the art.
Vibratory finishing apparatus has also been developed which utilizes a drive motor mounted on a fixed base and coupled to the eccentric weight shaft by means of a flexible coupling and universal joint. This arrangement is suitable only for apparatus utilizing a horizontal tub and a horizontally mounted eccentric weight shaft at the bottom thereof. Such apparatus does not undergo gyrational motion but only translational movement at low amplitude. Moreover, in such apparatus some power is dissipated in the universal joint. Additionally, the universal joint must be frequently replaced.
Another apparatus suitable only for use in connection with a horizontal tub and a horizontally mounted eccentric weight shaft is shown in Shiplov U.S. Pat. No. 3,680,266, which apparatus again does not undergo gyrational motion but only translational motion at low amplitudes. The pulley in Shiplov is moreover clearly inside his bearings inasmuch as his shaft is mounted in plate 22.
In the case of a vertically mounted rotating eccentric weight system, the amplitude of the gyrational movement of the ends of the shaft is so great that it would be virtually impossible to power the shaft by means of a stationary motor operating through a universal joint and certainly a pulley coupled to the end of the shaft.
This has been recognized in the prior art by experts in the field, for example, in Ferrara U.S. Pat. Nos. 3,570,192 and 3,693,298 in which the Applicant Ferrara, commenting upon gyratory finishing machines of the type here concerned, respectively states as follows:
"Conventionally, the vibratory mechanism is enclosed within a protective housing. Often, the unbalanced weights are mounted directly to the shaft of an electric motor, and the housing of the electric motor is mounted directly to the bowl. In such instances, it is commonly found that inadequate ventilation and moisture accumulation contribute to the rapid failure of the electric motor. In other instances, an electric motor or other prime mover is used to drive a separate shaft having the unbalanced weights. In such instances, it is difficult to provide a satisfactory coupling between the prime mover and the shaft because the shaft vibrates eccentrically when rotated. In any such instance, the load on the bearing means intermediate the shaft carrying the unbalanced weights and the housing is constantly unbalanced. Consequently, bearing wear is excessive and average bearing life is short." PA1 "Conventional vibratory finishing machines produce a vibratory movement of the vertical center shaft which is too violent to permit use of a drive belt arrangement thereby necessitating that the drive motor be mounted directly on the bowl assembly."
and
Accordingly, Ferrara, in his two patents, provided extremely complicated equipment to remedy the problems and shortcomings which were apparent to him as stated in the foregoing. The present invention, quite to the contrary of the experience of the prior art, as representatively expressed by Ferrara in his two foregoing identified patents, is based upon the discovery that the problems observed by Ferrara, as one skilled in the art, which made it difficult if not impossible to provide a satisfactory coupling between the prime mover and the central vertical shaft, because the shaft vibrates eccentrically when rotated in a gyratory machine of the present type and because the gyratory movement of the vertical center shaft is too violent to permit use of a drive belt arrangement, are problems which do not exist when a motor of ordinary type is coupled to flexible endless belt means and the drive means is located on the resiliently-mounted finishing chamber or on support means therefor, e.g., a central tubular housing for the vertical center shaft. From the foregoing, it is clear that the motor may be a universal motor which is rigidly attached either to the finishing chamber or to its support means, by which is included a portion of the housing within which the finishing chamber is contained or upon which the finishing chamber is supported.